HIGHLY SENSITIVE FAR INFRARED DETECTOR FABRICATED WITH HIGH TC BI-CA-SR-CU-O SUPERCONDUCTOR USING LASER INDUCED DEPOSITION TECHNIQUE

IN THE PROPOSED WORK, FEASIBILITY OF DEVELOPING AND CHARACTERIZING A HIGHLY SENSITIVE FAR INFRARED DETECTOR, BEYOND 1 MICRON WAVELENGTH REGION, USING A HIGH TC SUPERCONDUCTING BI-CA-SR-CU-O MATERIAL, IS EXAMINED. THE DETECTION PRINCIPLE IS BASED ON THE FACT THAT INCIDENT INFRARED RADIATION PRODUCES A VOLTAGE SHIFT ACROSS THE JOSEPHSON JUNCTION, WHICH CAN SERVE AS A USEFUL DETECTOR OUTPUT. THUS IN THE PRESENT WORK, SUPERCONDUCTING WEAK LINKTYPE JOSEPHSON JUNCTION WILL BE FABRICATED AND TESTED AS A USEFUL DETECTOR. BULK SUPERCONDUCTOR SAMPLES OF BI-CA-SR-CU-O WILL BE PREPARED BY SOLID STATE REACTION METHOD. SUBSEQUENTLY, SUPERCONDUCTING THIN FILM OF 3-5 MICRON THICKNESS, WILL BE DEPOSITED ON A SUITABLE SUBSTRATE (MGO) BY LASER INDUCED DEPOSITION TECHNIQUE. A MAJOR ADVANTAGE OF THE PROPOSED TECHNIQUE IS THAT DUE TO EXCELLENTSPATIAL QUALITY AND SHORT WAVELENGTH (0.248 MICRON) OF THE LASER, IT PROVIDES A PRECISE CONTROL OVER THE DEPOSITION PROCESS WITH SUBMICRON RESOLUTION. TO FORM A WEAK LINK, A PART OF THE SUBSTRATE SURFACE IS GROUND DOWN (OR ETCHED BY LASER) TO FORM A GROOVE OF ABOUT 5 MICRON DEEPPRIOR TO THE DEPOSITION. FOR DETECTION, INFRARED SIGNALS WILL BE MODULATED AND GUIDED THROUGH AN OPTICAL FIBER TO THE DETECTOR. IN PHASE I, DETECTOR PERFORMANCE IN TERMS OF RESPONSIVITY AND MINIMUM DETECTABLE POWER LEVEL (NEP) IN THE SPECTRAL REGION OF 1-10 MICRON WILL BE EVALUATED. THE RESPONSIVITY OF THE PROPOSED DETECTOR IS ESTIMATED TO BE 10(4)V/W, WHICH IS SEVERAL ORDERS (4-5) OF MAGNITUDE HIGHER THAN THE PRESENTLY AVAILABLE QUANTUM DETECTOR IN THE 3-12 MICRON SPECTRAL REGION.